... the Surround is changing back to Stereo (i.e., 2.0 PCM) despite still indicating Surround as the selected option. I must change it to Stereo and then back to Surround to get proper Dolby Digital via the HDMI connection to my Integra receiver. ...
My theory on this is that it is an HDMI handshake problem where the cablebox goes to AVR (5.1) to TV (2.0). I think HDMI reports back to the cable box that the TV can only do 2.0 regardless of the intermediate AVR. Users not using HDMI all the way through the chain probably don't have the issue; for example, those using Component video to the TV or Optical audio to the AVR, perhaps.
To test this, I put a Gefen HDMI Detective set (»www.gefen.com/kvm/ext-hd ··· _id=8005) at a hard coded EDID of 5.1/1080i immediately after the cable box and before my AVR. The idea was that the X1 would always see an EDID that supported 5.1. So far this has worked - overnight, while repowering the X1, and after restarting the X1. I'll keep an eye on it, but I think this was the issue and is solved by the Gefen Box - not cheap though - more of a test device - and it would be nice if the X1 box would simply retain the customer settings without trying to be so clever.
That fits with what I suggested earlier in the thread.
This seems to be very similar to infamous Motorola cable box HDMI issues.
The fix there actually involves a pretty cheap device. Just get an inexpensive powered 2-port HDMI switch and put it in between the TV and the receiver. No need to use the 2nd port for switching, you just need an active device in the chain. It helps keep the proper EDID alive. At least with Moto boxes putting it between the cable box and receiver actually made it worse. So people may need to experiment with these new Pace boxes.
It's a really cheap fix, so I hope someone tries it out.